1. Field of the Invention
The present invention relates to a liquid jet recording head for discharging droplets of recording liquid in an ink jet recording system.
2. Related Background Art
A liquid jet recording head used in an ink jet recording apparatus (liquid jet recording system) has generally a fine recording liquid discharge opening (hereinafter often referred to as an “orifice”), a liquid flow path, and an energy-generating device provided in the liquid flow path for generating energy for discharging the liquid. Such a liquid jet recording head is conventionally produced by forming a fine groove on a glass or metal plate by cutting, etching, or a like working method, and then bonding the grooved plate to another suitable plate to form a liquid flow path.
However, the working precision is limited in cutting or etching of the glass plate or the metal plate. Moreover, the liquid jet recording heads produced by such a conventional method do not necessarily have invariable flow resistances of liquid flow paths because of roughness of the inner flow path walls or distortion of the flow paths caused by nonuniform etching, whereby the recording characteristics of the produced liquid jet recording heads tend to vary disadvantageously.
Further, the cutting is liable to cause chipping or cracking of the plate to result in a lower production yield. On the other hand, the etching, which is conducted through many production steps, results in high production cost. Furthermore, a common disadvantage of the aforementioned conventional methods is difficulty in positional registration in bonding the grooved plate having the liquid flow paths to a cover plate having a discharge-energy-generating element such as a piezo element or electrothermal transducer element. Therefore, conventional methods are not suitable for mass production.
Production processes offsetting the above disadvantages are disclosed in Japanese Patent Application Laid-Open Nos. 57-208255, 57-208256, and 61-154947.
In the methods disclosed in the above Japanese Patent Application Laid-Open Nos. 57-208255 and 57-208256, a pattern of nozzles including ink flow paths and orifices is formed from a photosensitive resin material on a base plate on which discharge energy-generating elements have been formed, and thereon a cover plate like a glass plate is bonded. However, such a method involves the problems below:    (1) The adhesive for bonding the cover plate may penetrate into the ink flow path to deform the flow path.    (2) In cutting the base plate to form the ink discharge opening, cut chips may be brought into the ink flow path to render the ink ejection instable.    (3) A portion of the ink discharge opening may be chipped in cutting the base plate having a hollow for the ink flow path.
These problems lower the yield of production of the liquid jet recording heads, and render difficult the production of a multiple recording head which has a fine ink flow path structure having many ink discharge openings on a broad nozzle face.
Japanese Patent Application Laid-Open Nos. 61-154947 discloses a method for solving the above problems. In this method, an ink flow path pattern is formed from a soluble resin, the formed pattern is coated with an epoxy resin or the like, the epoxy resin is cured, the substrate is cut, and the soluble resin is removed by elution.
With progress of technique in recent years, the recording is required to be finer and more precise. To satisfy the requirement, one method is to decrease the cross-sectional area of the orifice, which requires working technique for a finer orifice. In the methods disclosed in the aforementioned Japanese Patent Application Laid-Open Nos. 57-208255, 57-208256, and 61-154947, the ink discharge opening is formed by cutting the ink flow path, thus the distance between the ink discharge pressure generating-element and the ink discharge opening depends on the cutting precision. However, since the cutting is conducted generally by a mechanical means such as a dicing saw, the high precision is not readily achievable, and the substrate may be chipped to cause ink discharge in a wrong direction to impair the quality of printing.
To solve the above problems, a method for producing a liquid jet recording head was disclosed by the inventors of the present invention, which comprises the steps of:    (1) forming an ink flow path pattern from a soluble resin on an ink discharge pressure-generating element having been provided on a base plate,    (2) forming a coating resin layer on the layer of the above soluble resin,    (3) forming an ink discharge opening in the coating resin layer, and    (4) removing the soluble resin layer by elution.
In the above process of producing the liquid jet recording head, the distance between the discharge energy-generating element and the orifice, the most important factor for the characteristics of the liquid jet recording head, can be controlled precisely with high reproducibility by a thin film coating technique exemplified by spin coating. The positional registration of the discharge energy-generating element to the orifice can be conducted optically by photolithography with high positional precision.
The methods disclosed in the aforementioned Japanese Patent Application Laid-Open Nos. 57-208255, 57-208256, and 61-154947, which employ oxygen plasma, use a resin composition having higher workability than glass or metals as the material for the liquid jet recording head. Japanese Patent Application Laid-Open No. 3-184868 discloses a cation-polymerized and cured product of an aromatic epoxy compound as a coating resin suitable for the method described in the above Japanese Patent Application Laid-Open No. 61-154947.
The liquid jet recording head is kept incessantly in contact with ink (generally mainly composed of water, and not neutral) in the environment of use. Therefore, the constituting members are required to be affected little by the recording liquid. Change of the dimension, deterioration of adhesion to the base plate, and decrease of mechanical strength of the constituting member should be prevented which are caused by water absorption of the constituting member from the ink during a long term of use.
Generally, a cation-polymerized cured epoxy resin has high crosslinking density and a high glass transition temperature to have excellent mechanical strength and adhesiveness. However, with the resin, the water absorption is not proportional to the crosslinking density, and the water absorbency reaches the minimum in a certain crosslinking range. Therefore the desirable properties of high strength and high adhesiveness are not necessarily consistent with the minimum water absorbency.
After comprehensive study on the above problems, it has been found by the present inventors that the water absorbency of the cured epoxy resin is lowered by curing the epoxy resin in the presence of, or by reaction with a compound having a fluorocarbon moiety by utilizing the low surface tension of the fluorocarbon moiety-containing compound.